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Adjust positions of non-end nodes in a line?

  • January 11, 2017
  • 3 replies
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I have the following issue:

A bridge and the road below, standard 2D lines, both have nodes with identical coordinates - i.e. they share a "node location". When I want to output this dataset to OSM XML, the writer creates a connection in this point, even though they are not connected in realit". I've tried to separate them by Z-coordinate, but that had no effect. Therefore, my guess is that it creates a "node cache" with the coordinates as key, which means they will share a node because they share a coordinate.

With this in mind, my solution would be to slightly adjust the position of these internal nodes that overlap. Probably with just a minor change(cm? mm?), the nodes will not be cached to the same location. However, I've got no idea how to A) access all non-start or non-end nodes of a line and subsequently B) slightly and randomly alter their position.

Best answer by redgeographics

An alternative approach would be to use the CoincidentPointOffsetter transformer from the FME Hub. Since it works on points only you'll have to deconstruct your lines and keep track of both a line id and a point id so you can later on reconstruct the lines using the PointConnector.

offset-points.fmw

Hope this helps.

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3 replies

itay
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  • itaySupporter
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  • January 11, 2017

Hi @fhilding, For A see the CoordinateExtractor, mode Specify Coordinate, Coordinate Index =-1 and for B you can use the RandomNumberGenerator to generate a value between 0.001 and 0.010 (if your data is in meters) to add to the last coordinate via the Offsetter transformer.

Hope this helps.

redgeographics
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  • redgeographicsCelebrity
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  • Best Answer
  • January 11, 2017

An alternative approach would be to use the CoincidentPointOffsetter transformer from the FME Hub. Since it works on points only you'll have to deconstruct your lines and keep track of both a line id and a point id so you can later on reconstruct the lines using the PointConnector.

offset-points.fmw

Hope this helps.

FME rocks! \m/
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  • fhilding
  • Author
  • January 12, 2017

I went the Python route on this, inspired by redgeographics. The following snippet did the trick:

(Although it corrects ALL internal nodes, the offset is so small that it's acceptable for the data provided.)

    line = feature.getGeometry()
    ptTupleList = line.getPoints()
    ptTupleListNoEnds = ptTupleList[1:len(ptTupleList)-1]
    randomDifference = 0
    while -0.01 < randomDifference < 0.01:
        randomDifference = random.uniform(-0.10,0.10)
    correctedPoints = []
    for point in ptTupleListNoEnds:
        point.setXYZ(point.getXYZ()[0]+randomDifference, point.getXYZ()[1], point.getXYZ()[2])
        correctedPoints.append(point)
    for i in range(len(correctedPoints)):
        line.setPointAt(i+1, correctedPoints[i].getXYZ())
    feature.setGeometry(line)
    #feature.setAttribute("corr",randomDifference)
    return feature

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